To provide a cutting blade unit capable of raising cutting efficiency by allowing a mobile blade to tightly attached to a fixed blade by uniform pressurization and energization, thereby showing excellent sharp performance for a long term.

The cutting blade unit includes: the fixed blade 40; the mobile blade 41; an blade holder 42 made of a metal plate for integrally supporting the both blades 40. 41; and a fixed blade holder 23 for supporting the fixed blade 40. The blade holder 42 integrally includes: attachment walls 70 for supporting the fixed blade 40; and a holding wall 71 for holding the fixed blade 40 and the mobile blade 41 with the cooperation of the attachment walls 70. Respective right and left pairs of first springs 74 and second springs 75 are arranged on the wall surface of the holding wall 71 opposing to the mobile blade 41. Spring force is made to be fixed by eliminating variation in bent shape and spring tip position. The first springs 74 pressurize the mobile blade 41 on a cutting blade slide surface 45 and the second springs 75 pressurize the mobile blade 41 on a free end slide surface 46.